Cathode-ray tube structure



June 21, 1960 L. T. MAY 2,942,129

CATHODE-RAY TUBE STRUCTURE Filed Aug. 27, 1954 2 Sheets-Sheet 1 INVENTOR. LAWRENCE MAY ATTORNEYS L. T. MAY

CATHODE-RAY TUBE STRUCTURE June 21, 1960 2 Sheets-Sheet 2 Filed Aug. 27,1954 INVENTOR. LAWRENCE T. MAY

2,942,129 CATHODE RAY TUBE STRUCTURE Lawrence T. May, Cedar Grove, N.J.,assignor to Allen B. Du Mont Laboratories, Inc., Clifton, N.J., acorporation of Delaware Filed Aug. 27, 1954, Ser. No. 452,526 9 Qlnims.(Cl. 313-85) This invention comprises improvements in cathode-raypicture tubes of the type characterized by fluorescent screens dividedinto a lar e number of dot-like elements. Fluorescent tubes-havingscreens of this type are especially adapted to color picturereproduction. As is known in this art tubes of this kind usually employforaminous masks between the electron guns and the fluorescent screens.The invention herein particularly relates to novel means for mountingthese masks within the tubes. The name dot type cathode-ray tube isfrequently applied to tubes of this nature.

An important object of this invention is to provide novel and improvedmeans for mounting the foraminous mask in dot-type cathode-ray tubes.

Another object of the invention is to provide a structure which isself-cleaning at the contact surfaces of the mounting elements for themask.

Still another object is to provide supports by means of which the maskcan be rapidly repositioned with precision.

Still another object of the invention is to provide an indexingstructure against which the mask is seated and spring loading means forefiecting firm and relatively rigid positioning of the mask against theindexing means.

Other and more detailed objects of thisinvention will be apparent fromthe following description of the embodiments thereof herein disclosed.

In the accompanying drawings,

Figure 1 is a view of a cathode-ray tube in accordance with thisinvention showing a portion of the envelope broken away and some of thestructure in cross-section and illustrating one form of this invention;

Figure 2 is an enlarged detail broken view of a mounting assembly unitfor the foraminous mask including an indexing and positioning element;

Figure 3 is a similar view of a modified form of structure;

Figure 4 is a similar view of a still further modified form ofstructure; and

Figure 5 is a similar View of a still further modification.

Generally speaking, the cathode-ray structure illustrated is of a typewell known in the art of color television. As illustrated, it includesan envelope having a plurality of electron gun structures mounted in theneck portion thereof. For a three color system three such guns areemployed and two of them, namely Mr and 1115 provide electron beams 122*and 12b for the red and blue colors respectively. The green electron gunis hidden behind those illustrated, but the beam therefor is illus-"trated at 12g. As is well understood in the art, the three elementalcolor electron beams are sharply deflected at the points l5'r, 15b and15g which are known in the art as'the apparent electron beam sources.These sources are relatively fixed throughout all movements of the outerends of the beams across the screen. These deflections are produced by amagnetic deflector of which the magnetic deflection coil 13 isdiagrammatically illustrated as an example. The glass envelope flaresinto a bulbous portion 16 which terminates in arim to which is weldedwith a vacuum-tight seal a metallic annulus 17. A dish or dome shapedfaceplate 19 completes the bulbous portion of the envelope and isprovided on its rim with a similar -rnetallic annulus 18 which is weldedthereto with a vacuum-tight seal. In the completed envelope thefaceplate 19 is secured to the bulbous portion 16 by welding the flangesof the annuli I7 and 18 together with a vacuum-tight seal. It is ofcourse understood that the completed envelope lil for the tube is highlyevacuated when ready foruse.

As is well understood in the art, a dot-type fluorescent screen 23 isformed on the inner face of the faceplate 19 in any convenient manner,such as that described by Joseph G. Koosman in his copending applicationSerial 150. 446,015, new Patent No. 2,833,954, filed July 27,

The entire assemblage of dots can be divided into several sets accordingto the color of the light to be emitted thereby. In present practicethere are three such sets with all of the dots of one set emitting redlight, all of the dots of the second set blue light, and all of the dotsof the third set green light. The dots of these three sets arepreferably interspersed, usually in a regular array. The dots of eachset comprise elemental deposits of different phosphors which emit lightof the three colors mentioned upon excitation by electrons. As is wellunderstood in place of this type of screen a homogeneous phospho'r layercould be employed by filtering white light through dot-like coloredfilter elements.

A foraminous mask 21, preferably domed, has a rim 22 which rests on theprotuberances or indexing elements 20 which are formed accurately andare accurately posi-.

tioned'on the inner face of the faceplate 19 The mask 21 is positionedso that it's rim 22 rests on these protuberances 20.

When the electron guns are energized they emitthe electron beams 12%,12b and 12g respectievly, which are caused to converge on' asmall areaof the foraminous mask 21 and pass through the apertures shown therein.When the parts are properly positioned, electron beam 12;- from the gun112- strikes an elemental phosphor area14r, which emits red light only.Similarly the electron beams 12!: and 12g fromthe guns 11b and 11gstrike phosphor dots 14b and 14g respectively and thereby respectivelycause the emission of blue and green light. As is known, the function ofthe mask 21 is to shade the dots in such a way that the respectiveelectron beams will strike the right dots, as explained above.

In order to assure optimum brightness, color purity, and the necessaryresolution the mask21 must be precisely positioned relative to the dotswhich make up the screen 23. Furthermore, as is clear from the abovementioned Koosman application, the mask 21 must be removed and preciselyrelocated in its original position several times in the process offorming a dot-type screen 23.

The importance of maintaining the original mask position is furtherstressed by the fact that these tubes must be baked at high temperaturesduring processing. At these temperatures the mask expands radially andthis must be accomplished Without warping. The further condition must bemet that when the tube is cooled the mask must be free to contract toits original dimensions and position, else by assuming some otherposition color purity and quality be adversely affected.

In order to provide a structure which will meet these conditions theforarninous disc 21 is provided with a rim 22. which is preferably givena shaped section like or similar to that shown, thereby insuring greateroverall rigidity in the disc. Around the periphery on the face or" thesection 22 aremounted the fixtures 24, one for each of the indexingelements 20, as suggested in Figure 2. The

fixture 24 is of U-shaped formation with the free side 'edgesthereofwelded to the face of the rim 22 so as to lie so as to form pointcontacts with these edges and to interlock therewith in order to indexthe mask 21 into position.

It is obvious that the fixture 24 can take other physical V forms solong as the type of supporting contact described above .is provided. Forexample, it is not necessary to use channel stock for the fixture 24;flat stock may be used instead, provided it is sufliciently thick toallow the tip of the protuberance to clear the surface of the rim 22, orprovided slots or indentations are formed in the surface of the rim 22to prevent the tip of the protuberances from resting thereon. Since themask expands and con tracts radially in the direction of the doubleended arrow 25 this movement will cause the sharp edges 26 and 27 toslide on the protuberances 20 cutting through any foreign matter whichmight be deposited thereon and allowing freedom of such radial movementwhile assuring precise repositioning.

Since, as a matter of stable geometry, three points of support for themask 21 will accurately determine the position plane thereof, and thesame number of slotted fixture-24 will be sufficient to index the mask21 so that it may be placed in only one position with respect to thefaceplate 19, there will normally be three protuberances 2i and threefixtures 24. However, in the interest of greater mechanical strengthmore than three mask supports can be employed.

An additional support structure for the mask 2-1 is shown in Fig. 3 inwhich the fixture 30 is in the form of a flat plate welded or otherwisesecured to the rim 22 and having an integral out-turned tab 31 which canbe longitudinally creased, if desired, to strengthen it. These fixtures30 are preferably spaced around the rim 22 intermediate the indexingfixtures 24 and serve to provide additionalspacing support forthe mask21. The tab 31 is preferably provided with a rounded end which will seaton the inner face of the faceplate 19.

In orderto hold the mask 21 positioned against the indexing means ofeither type above described, spring setting devices are provided.Referring to Figure 4 there is illustrated one type employing a wirespring 32 which is generally shaped like a hairpin to provide a pair ofparallel legs 33 and 34 which terminate with looped ends as shown. Thebent over or looped portion 36 of these springs is shaped to seat withinthe rim formation 22 at the closed end of the spring. The looped endsarearranged to seat on a radial inwardly projecting rim portion of theannulus 18. One of these springs is provided at each of the indexingpositions and shaped so that understress they will fit snugly on theirseats at each end and hold the disc 21 firmly in index position. Thesesprings strengthen the whole assembly and will permit easy removalduring processing.

Alternative spring structure is shown in Figure 5. In this embodimentthe springs 37 are formed of suitable flat stock and are given aslightly bowed shape longitudinally, as indicated at 38 in the figure.The upper end of the spring is provided with a pair of tabs 40 and 41and positioned to seat in apertures 44 and 46 respectively formed 'inthe rim 122 of the foraminous mask 121. The fixture 24 is the same asthat shown in Figure 2 and rests on the protuberance 20, as previouslyexplained. The other end of the spring is provided with end tabs 42 and43 which find a seat on the inner radial rim of the annulus 18. Theparts are positioned and the spring 37 is shaped so as to be stressed inuse, causing the mask 121' to be firmly indexed.

From the above description it will be apparent that the subject matterof this invention can take a number of different forms. It ispreferable, therefore, that the scope of this invention be limited bythe claims rather than the disclosure.

What is claimed is:

1. A cathode-ray tube comprising a glass faceplate, a plurality ofprotuberances on the inner surface of said faceplate near the peripherythereof, a foraminous mask 1,3, located within said tube substantiallyparallel to said faceplate, a reinforced rim on said mask, a pluralityof U-shaped members corresponding in number to the number of saidprotuberances and afiixed to the side of said rim proximal to, saidfaceplate, said U-shaped members pointing substantially in the radialdirection of said mask, said U-shaped members being spaced around saidrim to rest on said protuberances with the ends of said protuberanceslying within the open portion of said U- shaped members and bearingagainst both branches thereof.

2. The device of claim 1 in which said U-shaped members are formed fromchanneled material with the outer edges of both branches extending inthe same direction from the main portion of said U-shaped members.

3. The device of claim 2 in which said U-shaped members are aifixed tosaid rim by means of said outer edges.

4. A cathode-ray tube comprising a glass faceplate, a a

plurality of protuberances on the inner surface of said faceplate nearthe periphery thereof, a foraminous mask located within said tubesubstantially parallel to said faceplate, a plurality of U-shapedmembers correspond ing in number to the number of said protu'berancesand afiixed to the side of said rim proximal to said faceplate, saidU-shaped members being spaced around said rim to rest on saidprotuberances with the ends of said protuberances lying within the openportion of said U- shaped members and bearing against both branchesthereof, and a plurality of support legs afixed to said side of said rimbetween said U-shaped members, said legs extending down to make contactwith said inner surface of said faceplate;

5. The device of claim 4 in which said legs comprise flat plate basesaflixed to said rim with rounded end tabs extending substantiallyperpendicular thereto.

6. A cathode-ray tube comprising a glass faceplate, a

cylindrical wall attached to the periphery of said faceplate andextending upwardly therefrom, an inwardly extending rim at the upper endof said cylindrical wall, a plurality of protuberances on the innersurface of said faceplate near said periphery, a forarninous masklocated within said tube substantially parallel to said faceplate, areinforced rim on said mask, a plurality of U-shaped memberscorresponding in number to the number of said protuberances and affixedto the side of said rim proximal to said faceplate, said U-shapedmembers pointing substantially in the radial direction of said mask andbeing space around said rim to rest on said protuberances with the endsof said protuberances lying within the open portion of said U-shapedmembers and bearing against both branches thereof, a plurality of springmembers bearing against the lower surface of said inwardly extending rimand against the upper surface of said rim on said mask. 7

7. The device of claim 6 in which one of said spring members makescontact with the rim of saidmask in the region of each .of said U-shapedmembers.

8. The device of claim 7 in which said spring members are hairpin shapedand comprise two upwardly extending ends joined by a flat portionfitting within the reinforced rim of said mask.

9. The device of claim 7 in which said spring members comprise fiatspring stock having a bowed shape with each end having longitudinallyextending tabs at the outer corners thereof.

References Cited in the fileof this patent UNITED STATES PATENTS

